Democratic leaders this weekend implored attendees at the state party convention in San Diego to harness the energy and enthusiasm of 2008, casting the upcoming elections as pivotal moments that will determine the trajectory of the country for decades to come.

Sen. Dianne Feinstein said Saturday that the only way to maintain the firewall against Republican and tea party “extremism” is to re-elect President Barack Obama, return her to the U.S. Senate for another term and marshal the resources to regain control of the House of Representatives.

She was among dozens of speakers — including Gov. Jerry Brown, House Minority Leader Nancy Pelosi and Sen. Al Franken, D-Minn. — to paint an unfavorable picture of the alternative.

“Just think of the damage a Gingrich or a Romney or a Santorum would do if they reach the White House or if the tea party takes over Congress,” Feinstein said in a speech at the San Diego Convention Center.

“It would be no health care reform,” she added. “It would be no job program. No financial regulation. No effort to deal with climate change. No stem cell research. No reform of a broken immigration system. ... No woman’s right to choose. And a meat ax to Medicare and Social Security.”

It was the state convention here five years ago that set the stage for the elections of 2008, when Democrats rode a wave of victories in statehouses, Congress and the White House.

“We didn’t come to San Diego for the weekend,” Democratic state Attorney General Kamala Harris said in her speech Saturday. “We came here for the next generation.”

The prospects for a major Democratic triumph at the national level won’t be easy, political analysts said. They predicted that Democrats likely would have to turn out in numbers similar to the 2008 showing to wrest away enough seats to take control of both chambers of Congress.

“The long and short is right now Republicans are favored to hold the House,” said Larry Sabato, director of the University of Virginia’s Center for Politics. “It’s harder to be more precise because there are so many districts that haven’t been OK’d by the courts or the (U.S.) Justice Department.”

Gary Jacobson, a congressional expert and professor at the University of California San Diego, said: “They are going to have to hit a lot of inside straights to do it and that would include California.

“They are trying to recruit candidates, raise money and get the base enthused, so it’s traditional for them to express an optimistic outlook on their prospects.”

But the nation’s newfound rise in economic optimism, fragile as it may be, has turned what was an unlikely scenario for victory into an opportunity for Democrats to at least raise money and rally core voters.

At the convention, Pelosi, D-San Francisco, laid out a multistate plan that, if successful, would make her the first House speaker to return to the position since 1955.

She said California, Texas, Illinois, Florida and New York would bring the party within six seats of the needed 25-seat gain. The only one of those states where Obama is expected to campaign heavily is Florida.